Methods and apparatus for depositing pyrolytic coatings having a fade zone over a substrate and articles produced thereby

ABSTRACT

The present invention is directed to a method of and apparatus for forming a coating having at least one fade zone over a substrate. The method and apparatus include positioning a coating composition dispenser above a surface of a substrate with the coating composition dispenser oriented to dispense a coating composition spray generally normal to the surface of the substrate. A gas dispenser is also positioned above the surface of the substrate and adjacent the coating composition dispenser with the gas dispenser oriented to dispense a gas stream generally normal to the surface of the substrate. The coating composition spray and the gas stream are spaced from each other so as to develop an interference effect therebetween adjacent the surface of the substrate. Preferably the substrate is maintained at a temperature which pyrolyzes the coating composition. The interference effect directs the coating composition to deposit over the substrate as a coating having a fade zone. In an alternative embodiment of the present invention, a plurality of coating composition dispensers and gas dispensers may be positioned over the substrate to provide one or more coatings on the substrate, each of which possesses at least one fade zone.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed to a method of and apparatus forforming a coating having at least one fade zone on a surface of anarticle and, more particularly, to a method of and apparatus forpyrolytically depositing one or more metal oxide coatings having atleast one fade zone on a portion of a moving float ribbon of glass. Thepresent invention is also directed to articles having a coating formedover a surface of the article, which coating includes at least one fadezone, particularly articles made from the above-described coated floatglass ribbon.

2. Description of the Prior Art

As used herein, the term “fade zone” refers to an area or zone of acoated article, e.g. a coated substrate, having a first limit spacedapart from a second limit, in which a coating present over the substratewithin the zone gradually decreases in thickness, intensity and/ordensity from a first thickness, intensity and/or density at the firstlimit to a second lesser thickness, intensity and/or density at thesecond limit. The term also refers to an area or zone in which a coatingpresent over the substrate gradually decreases in thickness, intensityand/or density from a first thickness, intensity and/or density at afirst limit to an absence of coating over the substrate at a secondlimit. Such coatings may also be referred to as “graded” or “gradient”coatings.

It is known to form a coating having a fade zone over a substrate. Forexample, U.S. Pat. No. 3,004,875 to Lytle discloses applying a band ofmetal salt composition at an oblique angle toward an edge portion of asubstrate to be coated, using a shield to limit the area of applicationof the coating composition. The resulting band is of graduallyincreasing intensity from its boundary portion adjacent to the edge ofthe shield because of eddies that evolve beneath the shield near theedge of the shield during the coating operation.

Also, for example, U.S. Pat. No. 2,676,114 to Barkley discloses variousmethods of producing graded coatings by vacuum deposition usingmechanical barriers to apply graded coatings to glass sheets.

U.S. Pat. No. 3,305,336 to Browne et al. discloses a spray gun systemused in conventional spray techniques as opposed to electrostatic spraytechniques, for applying a film on a glass surface. The film is formedas a band having a major area of maximum intensity bordered by afade-out line that defines a fade-out area in which the transmittance ofthe film gradually and progressively increases until its value reachesthe clarity of the glass substrate.

U.S. Pat. No. 4,138,284 to Postupack and U.S. Pat. No. 4,208,446 toPostupack et al., disclose a method of forming a graded shade band on asubstrate by electrostatically spraying a dye composition past agrounded electroconductive shield or multiple grounded shield systemtoward a substrate to control the location of the cut-off line betweenthe coated and uncoated regions of the substrate and to limit the amountof dye deposited in the vicinity of the cut-off line to form a gradedcoating.

Forming coatings, particularly metal oxide coatings, by spray pyrolysisis also known. For example, U.S. Pat. Nos. 3,660,061; 4,719,126 and4,719,127, each of which are hereby incorporated herein by reference,describe the pyrolytic deposition of metal oxide films onto glasssurfaces.

A relatively complex apparatus for forming coatings by spray pyrolysisis described in U.S. Pat. No. 4,111,150, which is hereby incorporatedherein by reference. The apparatus is described as being able to obtainspecial effects in coatings, such as graded or varied thickness films byarranging sets of coating composition dispensers which are moved by acontinuous traveling chain over a conveyor to coat glass traveling onthe conveyor.

It would be advantageous to provide methods of and apparatus for formingpyrolytically deposited films or coatings having a fade zone, whichmethods and apparatus are in addition to those that are presentlyavailable and, more particularly, which do not require complex apparatusto obtain such a coating.

SUMMARY OF THE INVENTION

The present invention is directed to a method of forming a coatinghaving at least one fade zone over a surface of a substrate. The presentinvention is also directed to an article which includes a substratehaving a coating formed thereon, which coating includes at least onefade zone. Still further, the present invention is also directed to anovel apparatus for forming a coating having at least one fade zone overa surface of an article. In a preferred embodiment of the presentinvention, the coating is formed by the spray pyrolysis process.

The method for forming a coating having at least one fade zone over asurface of a substrate includes the steps of simultaneously directing aspray of a coating composition and a stream of a gas toward a surface ofa substrate. The spray of coating composition and the stream of gas aremaintained in spaced relation to one another such that an interferenceeffect adjacent the surface of the substrate is produced between thespray of coating composition and the gas stream wherein the interferenceeffect directs the coating composition to be deposited on the surface ofthe substrate as a coating having a fade zone. The method includes thestep of depositing the coating composition over the surface of thesubstrate to form a coating having a fade zone over at least a portionof the surface of the substrate.

More particularly, the present invention includes a method for forming acoating having at least one fade zone over a surface of a substratewhich method includes the steps of providing at least one coatingcomposition dispenser above a surface of a substrate, wherein thecoating composition dispenser is oriented to direct a spray of a coatingcomposition toward the surface of the substrate, providing at least onegas dispenser above the surface of the substrate, wherein the gasdispenser is oriented to direct a stream of a gas toward the surface ofthe substrate. The method includes the steps of activating the coatingcomposition dispenser to dispense a spray of coating composition andsimultaneously activating the gas dispenser to dispense a stream of agas. The spray of coating composition and the gas stream are maintainedin spaced relation to one another such that an interference effectadjacent the surface of the substrate is produced between the spray ofcoating composition and the gas stream wherein the interference effectdirects the coating composition to be deposited on the surface of thesubstrate as a coating having a fade zone. The method includes the stepof depositing the coating composition over the surface of the substrateto form a coating having a fade zone over at least a portion of thesurface of the substrate.

In an alternative embodiment of the present invention, the coatingcomposition dispenser may be interposed between a pair of gasdispensers, all of the dispensers being positioned above a surface of asubstrate wherein the spray of coating composition and the gas streamsare maintained in spaced relation to one another such that aninterference effect is produced adjacent the substrate surface betweenthe spray of coating composition and the gas streams, wherein thecoating composition is deposited over a surface of the substrate as acoating having a pair of opposed fade zones.

In yet another embodiment of the present invention a plurality ofcoating composition dispensers and gas dispensers may be provided abovethe surface of the substrate to provide a plurality of coatings on thesurface of the substrate, at least a portion of the coatings includingat least one fade zone. The present invention is also directed to amethod for providing a coating having at least one fade zone on one ormore discrete portions of a substrate surface.

The present invention is also directed to an article of manufacturewhich includes a substrate having at least one coating formed over asurface of the substrate, which coating includes at least one fade zone.In a preferred embodiment the substrate is glass, e.g. a glass floatribbon or an individual glass sheet, and the coating includes one ormore metal oxide coatings, at least one or which includes a fade zone.

The present invention is also directed to an apparatus for depositing acoating having at least one fade zone on the surface of an article,which apparatus includes a device for moving an article in a downstreamdirection along an article movement path lying in a generally horizontalplane, a coating composition dispenser positioned in spaced relationabove the article movement path wherein the coating compositiondispenser directs a spray of coating composition downward toward thearticle movement path, and a gas dispenser positioned in spaced relationabove the article movement path and spaced from the coating compositiondispenser along a line generally perpendicular to the longitudinal axisof the article movement path wherein the gas dispenser directs a gasstream downward toward the article movement path. The coatingcomposition dispenser and the gas dispenser are positioned relative toone another so as to produce an interference effect between the spray ofcoating composition and the gas stream which interference effect directsthe coating composition to be deposited as a coating having at least onefade zone when directed toward the surface of an article conveyed alongthe article movement path.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an apparatus for depositing a coatinghaving a fade zone over a continuous ribbon-like substrate.

FIG. 2 is a top plan view of the substrate of FIG. 1 illustrating theformation of an interference effect between a coating composition sprayand a gas stream.

FIG. 3 is side elevational view of a portion of the substrate of FIG. 1illustrating the deposition of a coating having a fade zone thereon.

FIG. 4 is a perspective view of an apparatus for depositing a pluralityof coatings having a plurality of fade zones over the surface of acontinuous ribbon-like substrate, and more particularly an apparatus fordepositing two spaced coatings over a surface of a substrate, each ofthe coatings including a pair of opposed fade zones.

FIG. 5 is a top plan view of the substrate of FIG. 4 illustrating theformation of an interference effect between a plurality of coatingcomposition sprays and a plurality of gas streams to deposit two spacedcoatings over the surface of the substrate, each coating having a pairof opposed fade zones.

FIG. 6 is a side elevational view of the coated substrate of FIG. 5illustrating a pair of opposed fade zones of each of the two spacedcoatings deposited over the surface of the substrate.

FIG. 7 is a perspective view a continuous ribbon-like substrate having apair of spaced coatings deposited over a surface of the substrate, eachcoating including a pair of opposed fade zones, illustrating thesectioning of the coated substrate into subsections, each subsectionhaving a single coating having a single fade zone deposited over asurface of the subsection.

FIG. 8 is a perspective view of an automotive vehicle incorporatingcoatings having a gradient fade zone in the windshield, sidelights andbacklight of the vehicle.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In order to appreciate this invention and its use, it is convenient toconsider it in the context of the processes and apparatus in which itmay be employed. The invention will be understood more clearly in thelight of the description of illustrative embodiments that follows inwhich in the drawings that form part of the description, like referencenumerals refer to like elements.

Referring now to FIG. 1, there is illustrated a coating station 20 fordepositing a coating having at least one fade zone over a substrate orworkpiece 31. For the sake of brevity, the workpiece 31 over which thecoating having the fade zone is deposited is identified in the followingdiscussion as a glass float ribbon, however, as may be appreciated thepresent invention is not limited to glass float ribbons, nor even toglass substrates or ribbon-like substrates generally, but includes anysubstrate over which a coating having a fade zone is required ordesired. The coating station 20 includes a coating apparatus 22positioned over conveying facility 24, e.g. but not limiting to theinvention a plurality of spaced conveying rollers 30 as illustrated inFIG. 1. In accordance with a preferred practice, at the upstream end ofthe coating station 20 designated by the numeral 26 is a glass removaland conveying facility extending from a float forming chamber (notshown) in which glass is formed into a continuous ribbon by flotation onmolten tin. Thus the workpiece 31 entering and passing through thecoating station 20 in the preferred practice of the invention is a glassribbon which is sufficiently hot, e.g. about in the range of about 1000°F. to about 1500° F. (about 538° C. to about 815° C.), to provide thenecessary heat for high-temperature pyrolysis of coating reactantsdeposited on the glass ribbon in the coating station 20 as describedhereinafter. At the downstream end of the coating station designated bythe number 28 may be an annealing lehr in which the glass ribbon iscontrollably cooled to anneal the ribbon and reduce internal stresseswithin the glass to acceptable levels e.g. for cutting of the ribbon.The coating station 20 is preferably located between a float formingchamber and an annealing lehr in the manner illustrated and described inU.S. Pat. No. 3,660,061 to Donley et al., hereby incorporated herein byreference. Nevertheless, it should be recognized that this invention maybe employed in conjunction with a process for treating discrete sheetsor plates of glass that are heated in a furnace and conveyed through thecoating station 20 and then through a tempering quench to temper theglass or through an annealing lehr to anneal it. It should also berecognized that the movement of the workpiece 31 with respect to thecoating station 20 is relative, and that in an alternative embodiment ofthe present invention the workpiece 31 may be kept stationary while oneor more coating stations 20 travel over one or more surfaces of theworkpiece 31 to provide one or more coatings having a fade zone over oneor more surfaces of the workpiece 31.

With continued reference to FIG. 1, the coating station 20 includes afirst exhaust assembly 32 located upstream and spaced from a secondexhaust assembly 34 with coating equipment, described in more detailbelow, therebetween. The exhaust assemblies 32 and 34 are connected attheir upper ends to an external exhaust facility (not shown) todischarge unwanted air and products of vaporization and reaction fromthe coating station 20. The coating equipment includes a coatingcomposition dispenser 36 and a gas dispenser 38, each of which ispositioned over workpiece 31. Each dispenser 36, 38 is oriented todispense respective materials, described in more detail hereinafter,toward and generally normal to the plane of conveyance of workpiece 31,i.e. toward the surface 39 of the workpiece 31. The gas dispenser 38 isspaced from coating composition dispenser 36 along a line which isgenerally perpendicular to the longitudinal axis of the plane ofconveyance of workpiece 31, as shown in FIG. 1. Such a spatial relationenables the development of an interference effect between the respectivematerials dispensed by coating composition dispenser 36 and gasdispenser 38, which causes the coating composition to be deposited witha fade zone, as describe in more detail hereinafter.

The coating composition dispenser 36 dispenses a coating composition 40toward and over at least a portion of the workpiece 31 as it travelsthrough the coating station 20 on the conveying facility 24 in thedirection of the arrow 42. Preferred coating composition dispensers 36are spray dispensers which spray atomized liquid coating compositions.The coating composition dispenser 36 is preferably selected to dispensethe coating composition 40 in a fan or cone-shaped spray onto at least aportion of the surface 39 of the workpiece 31 in a generally circular orelliptical spray pattern. An elliptical spray pattern 44 is shownintersecting the surface of workpiece 31 in FIG. 2. The size of thespray fan or cone-shaped spray provided by the coating compositiondispenser 36 and the distance between the coating composition dispenser36 and the workpiece 31 are coordinated so that the circular orelliptical spray pattern covers a desired portion of surface 39 ofworkpiece 31. Coating pressures and volumes through coating compositiondispenser 36 are selectably controlled to deposit a desired or requiredcoating pattern and thickness on the surface 39 of the workpiece 31.

The gas dispenser 38 dispenses gas 46 in a stream toward the workpiece31 that, similar to the coating composition 40, intersects the surface39 of the workpiece 31. The term “stream” as used herein includes anyflow of gas 46, however a generally circular or elliptical pattern isparticularly preferred to develop the interference effect described inmore detail below. An elliptical gas stream pattern 48 is shownintersecting a surface of workpiece 31 in FIG. 2. The size of the gasstream provided by the gas dispenser 38 and the distance between the gasdispenser 38 and the workpiece 31 are coordinated so that the gas streamcovers a desired or required portion of the surface 39 of workpiece 31.The gas may include either a gas which does not react chemically withcoating composition 40 or a gas which reacts chemically but favorably toprovide a coating 47 over the surface 39 of the workpiece 31. Preferredgases include air, inert gasses and mixtures thereof. Inert gasesinclude but are not limited to nitrogen and the noble gasses, includingbut not limited to argon and krypton, and mixtures thereof.

It is an important aspect of the present invention that the coatingcomposition dispenser 36 and the gas dispenser 38 are positioned overthe workpiece 31 and relative to each other such an interference effectis created between the coating composition elliptical spray pattern 44and the gas stream adjacent the surface 39 of the workpiece 31, which inturn, causes the coating composition 40 to be deposited over surface 39of workpiece 31 as coating 47 having a fade zone 49, as shown in FIGS. 2and 3. More particularly, as illustrated in FIG. 3, the coating 47 isthickest over the area of workpiece 31 where the coating compositionspray pattern 44 is subjected to little or no interference effect as itis deposited onto the surface 39. The coating 47 decreases in thickness,or fades in the area where the interference effect is observed until nocoating 47 is deposited over the surface 39 of the workpiece 31.

The formation of a fade zone is facilitated where the workpiece 31 is ata sufficiently high temperature which forms a thermal barrier over thesurface 39 of the workpiece 31. An important factor in establishing thetemperature at which the thermal barrier will form is the boiling pointof the coating composition. Generally, as the carrier or solventcomprises the greatest percentage of the coating composition, theboiling point of the carrier or solvent will have the predominant effecton the formation of a thermal barrier. Where the temperature of theworkpiece 31 is above the boiling point of the coating compositionparticularly the carrier or solvent of the coating composition, at leasta portion of the droplets of coating composition approaching the surface39 of the workpiece 31 begin to vaporize. This vaporization processproduces expanding gasses which operate to provide an upward force thattends to counter or prevent the deposition of at least a portion of thecoating composition particles on the surface 39 of the workpiece 31operating to suspend these particles of coating composition above thesurface 39 of the workpiece 31 until they are either deposited orremoved as discussed in more detail below. This phenomenon may bereferred to as thermophoresis. For example, where the carriercomposition is primarily aqueous, the boiling point of the solvent orcarrier may generally be about 100° C. (212° F.) and it is expected thatthe thermal barrier will be formed at about this temperature.

The temperature of the workpiece 31 may be elevated to form the thermalbarrier by any means known in the art, e.g. but not limited to aconventional oven and the like. Alternatively, the process ofmanufacturing the workpiece 31 may involve a heating operation whichimparts sufficient heat to the workpiece 31 to form the thermal barrier,e.g. the process of melting glass frit and forming the glass floatribbon over the molten tin bath.

The presence of the thermal barrier is believed to facilitate theformation of the fade zone for the following reason. Particles ofcoating composition 40 directed toward the surface 39 of the workpiece31 by coating composition dispenser 36 typically include particles ofvarying mass and momentum traveling in several vectors, the majority ofwhich are generally directed toward the surface 39 of the workpiece 31.These particles are carried by momentum and/or the acceleration due togravity toward the surface 39 of the workpiece 31. These particles tendto deposit in the greatest concentration in and about the area definedby the intersection of the coating composition spray pattern, e.g.elliptical spray pattern 44, and the surface 39 of the workpiece 31. Theremaining particles tend to deposit themselves along a gradientextending generally outwardly along the surface 39 of the workpiece 31in a 360 degree pattern from the above described area of intersection.However, as the workpiece 31 is conveyed by conveying facility 24 alongthe direction shown by arrow 42, at least along the longitudinal axis ofthe plane of conveyance of the workpiece 31, little or no gradienteffect is observed in the coating 47 for that portion of the surface 39of the workpiece 31 over which the coating 47 is deposited due to thecontinuous passing of the surface 39 of the workpiece 31 under the spraypattern 44. It is possible for a gradient effect to be observed along aline generally parallel to the surface 39 of the workpiece 31 whichextends generally perpendicular to the plane of conveyance of theworkpiece 31, i.e. across the float ribbon. Where the thermal barrier ispresent over the surface 39 of the workpiece 31, e.g. such as during thepyrolysis process, it tends to counter or prevent the deposition ofthese particles on the surface 39 of the workpiece 31 by providing agenerally opposite force to that provided by momentum and theacceleration of gravity as described above. Between these competingforces, only those particles of coating composition having sufficientmomentum or mass to overcome the upward force provided by the thermalbarrier are able to deposit themselves on the surface 39 of theworkpiece 31. Those particles having insufficient mass or momentum aresuspended by the thermal barrier above the surface 39 of the workpiece31, and remain so suspended until they are either removed by exhaustassemblies 32 or 34 or are able to overcome the upward force of thethermal barrier by either the operation of gravity, dissipation of thethermal barrier by cooling, or both. Where no interference effect ispresent, i.e. where there is no gas stream 48, these suspended particleswill travel considerable distances across the workpiece 31 and depositthemselves in a very random fashion, forming a gradient but heavilymottled or splotchy appearing coating 47 across the workpiece 31, i.e.along a direction generally perpendicular to the longitudinal plane ofconveyance of the workpiece 31. Where gas stream 48 is provided and theinterference effect is produced, all or at least a majority of thesesuspended particles of coating composition 47 are constrained fromtraveling across the workpiece 31, and are removed by exhaust assemblies32 and 34, resulting in the formation of a controlled, evenly appearingfade zone 49 for the coating 47 across the workpiece 31 as illustratedin the figures, particularly FIG. 3. The unwanted deposition of coatingcomposition 40 over certain areas of the surface 39, i.e. the areabeyond the fade zone 49, is thus prevented. Further, the efficiency ofthe coating process is increased because no additional steps arerequired to remove coating composition 40 from areas of the substratewhere its deposition was not intended to occur.

As may be appreciated, even in the absence of a thermal barrier, theabove described interference effect may be employed to provide acontrolled, evenly appearing fade zone. However, the efficiency of theprocess is somewhat reduced because the portions of the surface 39within the coating station 20 and immediately upstream and downstream ofthat portion of the surface 39 which is directly under the gas stream 48at any given instant, are subject to the immediate deposition of theparticles of the coating composition. The deposition is immediate due tothe absence of a thermal barrier which when present tends to suspend theparticles as described above. The swirling coating composition particlesin the process of being drawn over the workpiece 31 toward exhaustassemblies 32 and 34 can immediately deposit anywhere on the surface 39of the workpiece 31 when there is no thermal barrier to force the abovedescribed particle suspension, even over those portions of the surfaceof workpiece 31 where such deposition is not desired, such as thatportion of the surface 39 extending beyond the fade zone. This somewhatlimits the ability of the interference effect to control or direct thedeposition of coating composition particles on the surface 39 of theworkpiece 31, particularly for that portion of the surface 39 outsidethe coated portion or the fade zone, where no coating composition 40 isrequired or desired. The efficiency of the process may be somewhatreduced, as for example, where additional steps are required to removecoating composition 40 from areas of the surface 39 of the workpiece 31where its deposition was not intended to occur.

As described above, the respective patterns of the gas stream and thespray of coating composition may have any geometric shape e.g. circularor elliptical, provided the interference effect is producedtherebetween. Furthermore, the interaction between each of therespective patterns of gas stream and spray of coating composition maybe employed to provide coatings 47 having fade zones with a variety ofcharacteristics.

For example, where the respective patterns are elliptical, having amajor axis and a minor axis, the major axis of each ellipse may form anyangle with the longitudinal axis of the plane of conveyance of theworkpiece 31. Where the major axis of the elliptical gas stream 48 andthe major axis of the coating composition spray pattern 44 are eachalong the same line and that line is generally perpendicular to thelongitudinal axis of the plane of conveyance of the workpiece 31 acoating 47 having a relatively wide fade zone having a slightly mottledappearance in the fade zone is produced. It is believed that eddycurrents and/or areas of turbulent air flow in the area where theinterference effect is observed causes the above described mottlingeffect.

Alternatively, for example, where the major axis of the ellipse of therespective elliptical patterns of the gas stream 48 and coatingcomposition spray pattern 44 are each generally parallel with each otherand with the longitudinal axis of the plane of conveyance of theworkpiece 31 and spaced from each other along a line generallyperpendicular to the longitudinal axis of the plane of conveyance of theworkpiece 31, a coating 47 having a relatively narrow fade zone may beproduced.

In yet another alternative embodiment, it has been found that theformation of eddy currents and/or areas of turbulent air flow aresignificantly reduced where the coating composition 40 spray pattern andthe gas stream are both elliptical and where the major axes of eachellipse are generally parallel with each other and lie along a linewhich is at an approximately 45 degree angle from the longitudinal axisof the plane of conveyance of the workpiece 31. This is illustrated inFIG. 2 where the major axis 50 of elliptical spray pattern 48 of gas 46is at an approximately 45 degree angle 52 with the longitudinal axis ofthe plane of conveyance 54 of the workpiece 31. Similarly, the majoraxis 56 of the elliptical spray pattern 44 of the coating composition 40is at an approximately 45 degree angle 58 with the longitudinal axis ofthe plane of conveyance 54 of the workpiece 31, with the major axesparallel to one another. In this embodiment, a relatively wide fade zoneis formed on the workpiece 31, having a gradual or evenly appearing fadezone with no mottling. It has been found that when the respective gasstream and coating composition spray patterns are applied in thisfashion with the coating composition dispenser 36 and gas dispenser 38generally balanced in terms of operating pressures, operating volumesand spaced distances from the workpiece 31, that a coating 47 having adesirably gradual, evenly appearing fade zone with no mottling or abruptfade zones or draw lines may be produced.

The present invention is not limited to forming a single coating 47having a fade zone over a substrate, but includes the formation of morethan one such coating. For example, a plurality of coatings 47 eachhaving a fade zone may be deposited over surface 39 of workpiece 31where a plurality of paired coating composition dispensers 36 and gasdispensers 38 are positioned upstream and/or downstream of each otherbetween exhaust assemblies 32 and 34. Also for example, a plurality ofcoatings 47 each having a fade zone may be deposited over surface 39 byproviding a plurality of coating stations 20 placed downstream orupstream of each other in succession over the conveying facility 24. Inthese embodiments of the present invention, a plurality of coatings,each having a fade zone, may be deposited on top of one another as theworkpiece 31 moves downstream along its plane of conveyance. Inaddition, conventional coating stations (not shown) which form coatingswithout a fade zone may be intermixed with the plurality of coatingstations of the present invention to form a mixture of coatings over thesubstrate, a portion of which may include a fade zone and a portion ofwhich do not include such a fade zone.

In an additional embodiment of the present invention, two or moreseparate portions of the surface 39 of the workpiece 31 may each besimultaneously overcoated with a coating 47, wherein one or more of thecoatings includes at least two fade zones. Such an embodiment isillustrated in FIG. 4. Referring now to FIG. 4, there is shown afacility for preparing coated glass 60 which is in most respects similarto that of FIG. 2 with like elements bearing like reference numerals,but which includes coating station 62 which includes two coatingcomposition dispensers 36 disposed between three gas dispensers 38 allof which are spaced along a line generally perpendicular to the plane ofconveyance of workpiece 31. In a preferred embodiment, the gas streamspray patterns 48 and the spray patterns of the coating composition 44are elliptical in shape with the respective major axes 50 and 56parallel with each other and positioned at about a 45 degree angle withthe longitudinal axis of the plane of conveyance of the workpiece 31 asillustrated in FIG. 5. The coating composition dispensers 36 and gasdispensers 38 are each spaced from one another to provide interferenceeffects with a minimum of eddy current or turbulent flow which resultsin the deposition of two coatings 64 over the surface 39 of substrate31, each coating 64 having a pair of opposed fade zones 49, asillustrated in FIG. 6.

Illustrated in FIG. 7 is an indexing system in which workpiece 31 havingtwo coatings 64 deposited thereon, each of which has at least two fadezones 49, is indexed or cut by a cutting apparatus (not shown) intosub-parts 66, 68, 70 and 72, each of which includes a coating 64 havinga single fade zone 49 thereon. While the embodiment illustrated in FIGS.4 and 5 include two coating composition dispensers 36, as may beappreciated the present invention is not limited thereto, and severalcoating composition dispensers 36 interposed between gas dispensers 38in the manner shown in FIGS. 4 and 5 may be used to provide any numberof coatings 64 over a workpiece 31.

As may be appreciated, the coating composition 40 is not limiting to thepresent invention, may be any coating composition known in the artcapable of being sprayed toward the workpiece 31 and which is subject tothe formation of the interference effect in the presence of gasdispenser 38. Coating compositions capable of pyrolytic deposition arepreferred. Particularly preferred are metal oxide coating compositionssuch as disclosed in U.S. Pat. No. 3,660,061 at column 6, line 45,through column 8, line 25; U.S. Pat. No. 4,719,126 at column 2, line 18,through column 4, line 60, and U.S. Pat. No. 4,719,127 at column 2, line16, through column 6, line 14, each of which is hereby incorporatedherein in their entirety.

Non-limiting examples of selected parameters within which the presentinvention has been found to be effective will now be described. For manycoating applications, coating composition dispenser 36 may include astandard atomizing spray nozzle having a gas feed, typically an airfeed, which air feed may be operated at a pressure within the range ofabout 30 to 60 pounds per square inch gauge (psig), with a volume flowwithin the range of about 2 to 20 standard cubic feet per minute (scfm)(57 to 570 standard liters per minute (slpm)), preferably in the rangeof about 3 to 6 scfm (85 to 170 slpm). The coating composition isdispensed through the nozzle at a fluid flow rate of about 25 to 200milliliters (0.8 to 6.8 fluid ounces) per minute at a pressure of about1 to 20 psig. Coating composition dispenser 36 may be operated at anydistance from the workpiece 31 to provide a desired coating thicknessand coated area that provides an acceptable fade zone. A distance ofabout 10 inches (25.4 centimeters) has been found to be acceptable toprovide a coating 47 in the range of about 500 to about 1000 Angstromsthick at its thickest point, having a relatively gradual fade zone,where the coating 47 including the fade zone, is about 9 inches (22.9centimeters) wide where the gas dispenser is simultaneously employed asdescribed hereinafter. The pressure at gas dispenser 38 operates iswithin the range which, in combination with its spacing from theworkpiece 31 and from coating composition dispenser 36, provides adesirable interference effect to produce an acceptable fade zone. Forexample, gas dispenser 38 may include a standard spray nozzle operatedwith an air pressure of about 30 to about 60 psig at a volume flow ratewithin the range of about 2 to 20 scfm (57 to 570 slpm), more preferablywithin the range of about 3 to 6 scfm (85 to 170 slpm) when spaced abovethe workpiece 31 at a distance of about 10 inches (25.4 centimeters).The spacing of gas dispenser 38 from coating composition dispenser 36may be varied to provide the optimum fade zone for a given application,but a spacing having a distance of about 8 inches (about 20.3centimeters) along a line generally perpendicular to the longitudinalaxis of the plane of conveyance of the workpiece 31 has been found toprovide the acceptable fade zone described above for a gas dispenser 38and a coating composition dispenser 36 operated within the abovedescribed operating parameters.

The rate of movement of workpiece 31 along its plane of conveyance maybe varied in accordance with the above described flow rates to provide acoating of desired thickness. Within the above range of parameters, aline speed within the range of about 100 to 600 inches per minute (about254 to about 1524 centimeters per minute) has been found to beacceptable to provide coatings, particularly pyrolytically depositedmetal oxide coatings about 500 to 1000 Angstroms thick at the thickestpoint, when coating composition 40 included about a 10 to 25 percentsolids concentration of a metal acetylacetonate in an aqueous suspensiondispensed over workpiece 31 when it was maintained within thetemperature range of about 1000° F. to 1500° F. (about 538° C. to about815° C.).

The foregoing parameters and the given ranges are meant to beillustrative and non-limiting. However, it is preferred that whateveroperating parameters are selected, the following interrelationships areobtained. Referring now to FIG. 3, a side elevational view of the spraypattern of coating composition 40 and the gas 46 is shown. As may beappreciated, while previously described generally as fan-like orcone-shaped, each of the spray patterns forms what may be moreparticularly referred to as a bell-shaped curve, with outer edges of thepatterns forming a generally parabolic curve. When the coatingcomposition dispenser 36 and the gas dispenser 38 are spacedsufficiently above the surface 39 of the substrate 31, each of outeredges of their respective spray or flow patterns eventually flows alonga flow line which is essentially vertical and which intersects thesurface 39 of the substrate 31 generally normal to the surface 39. Atthis point, each of the respective flow patterns impinges the substrate31 over a surface area which does not appreciably change with increaseddistance between the respective dispensers and the substrate 31. Thusthe preferred minimum distance that coating composition dispenser 36 andgas dispenser 38 are maintained above the surface 39 of the workpiece 31is that distance which enables each of outer edges of the bell-shapedcurves of the respective spray patterns to intersect the surface 39generally normal to the surface 39. While a greater distance may beselected, it is generally unnecessary and may require greater operatingpressures and/or volumes to ensure adequate coating.

Upon selecting the appropriate range for the distance to maintain thecoating composition dispenser 36 and gas dispenser 38 above the surface39 of the workpiece 31 as described above, the respective dispensingpressures and volumes must be selected with a range that is bounded asfollows. The upper limit for the pressure and volume for this distance,is that pressure and volume for the coating composition dispenser 36which forces all or nearly all of the coating composition particles tobe forced through the thermal barrier and to deposit on the surface 39of the substrate 31, thus eliminating suspension of coating compositionparticles above the surface and the desired interference effectdescribed above, preventing the formation of a fade zone. The upperlimit of the pressure and volume for this distance for the gas dispenser38 is that pressure and volume which creates such turbulent flow thatthe interference effect is similarly destroyed, similarly preventingformation of the desired fade zone. The lower limit of the pressure andvolume for this distance for the coating composition dispenser 36 isthat pressure and volume which is so low that insufficient coatingcomposition is directed toward the surface providing too thin of acoating on the substrate. The lower limit of the pressure and volume forthe gas dispenser 38 at this distance is the pressure and volume whichis insufficient to form the interference effect, generally resulting inthe deposition of coating composition particles over all or nearly allthe surface 39 of the workpiece 31, preventing the formation of thedesired fade zone.

Having selected the distance of the respective dispensers 36 and 38above the surface 39 of the substrate 31 in accordance with theforegoing, and the respective operating pressures and volumes within theranges as described, the spacing between the respective dispensers 36and 38 along a line generally perpendicular to the longitudinal axis ofthe plane of conveyance the workpiece 31 may be selected within therange that provides the desired interference effect. The interferenceeffect can be selected to produce among other effects, a generally evenfade zone, or a mottled less uniform fade zone or to provide a visibleline of demarcation between the coated and uncoated portions of thesurface 39 of the substrate 31. The spacing between the respectivedispensers 36 and 38 to obtain the desired interference effect is alsoaffected where either of the respective spray patterns' geometric shapesare other than circular. For example, as described above, it has beenfound with the present invention that to obtain a generally even fadezone where the respective gas and coating composition spray patterns areelliptical having a major and minor axis, the major axes of eachrespective elliptical spray patterns are preferably aligned parallel toeach other and at about a 45 degree angle from the longitudinal plane ofconveyance of the workpiece 31. In general, reducing the spacing betweenthe dispensers 36 and 38 while maintaining all other factors constantresults in the formation of a clear draw line of demarcation between thecoated and uncoated portions of the surface 39 of the substrate 31 andmay result in the formation of a mottled, uneven fade zone. Similarly,in general, increasing the spacing between the dispensers 36 and 38while keeping all other factors constant eventually results in thedisappearance of an interference effect whereupon the coatingcomposition particles are deposited over all or nearly all the surface39 of the workpiece 31, preventing the formation of the desired fadezone.

As may be appreciated, the present invention is not limited to anyparticular application, and may be used where any coating having a fadezone is desired over any substrate. However, in a particularly preferredembodiment, the present invention is employed to provide a pyrolyticallydeposited coating having a fade zone over a substrate, particularly aglass substrate.

By way of non-limiting examples, the present invention is particularlyuseful for forming shade bands, privacy bands/coatings and/ordecorative/aesthetic bands/coatings having fade zones over glasssubstrates such as the glass substrates used in land, sea, air and spacevehicles and in architectural structures such as buildings and the like.As used herein the term “shade band” refers that portion of a glasssubstrate coated with one or more coatings which function to reduce theamount of light energy, particularly visible light energy, transmittedthrough the glass substrate. Shade bands are commonly employed forexample, along a portion of an automobile windshield, particularly nearthat portion of the windshield adjacent the roof line of the vehicle, toreduce the amount of sunlight transmitted through the windshield toprovide a shaded band for the comfort of the vehicles occupants. As usedhere the term “privacy band” or “privacy coating” refers to that portionof a glass substrate coated with one or more coatings which function toprevent or reduce the ability to view the interior of the vehicle orbuilding through the glass substrate from a position exterior of thevehicle or building. Where such a coating or coatings is/are presentover only a portion of a glass substrate it may be referred to as aprivacy band. Where such a coating or coatings is/are present over anentire glass substrate, as for example, an automobile sidelight, it maybe referred to as a privacy coating. Privacy coatings and privacy bandsmay be employed for example, on the sidelights and backlights ofautomotive vehicles to provide privacy for the vehicle's occupants. Asused herein, the term “decorative/aesthetic bands/coatings” refers to“bands” or “coatings” as those terms are described above which functionto provide a decorative or aesthetic appearance to the glass substrate.While such bands or coatings may incidentally provide shading orprivacy, the primary function of the decorative/aesthetic coating orband is to provide the decorative or aesthetic function described above.Bands or coatings which by design perform mixed privacy, shading and/oraesthetic functions may also be employed for certain applications.

In each of the above described shade band/coating, privacy band/coatingand/or decorative/aesthetic band/coating applications, the presentinvention may be employed to provide privacy, shading and/or aestheticbands/coatings having a fade zone between a first portion of the glasssubstrate coated with the privacy, shading and/or aestheticbands/coatings and a second portion of the glass substrate (or ofadjacent glass substrates) which is/are not coated with the privacy,shading and/or aesthetic band/coating.

For example, referring now to FIG. 8 there is shown an automotivevehicle 80 which includes windshield 82, backlight 84 and side lights86, 88 and 90. Windshield 82 includes shade band 92 which includes fadezone 49 which shade band 92 is formed as a coating deposited on asurface of windshield 92 in accordance with the present invention. Theshade band 92 may be formed on either the interior or exterior surfaceof windshield 92. Similarly, backlight 84 shown in phantom, includesshade band 94 which includes fade zone 49. Shade band 94 is formed as acoating deposited on a surface of backlight 84 in accordance with thepresent invention. The shade band 94 may be formed on either theinterior or exterior surface of backlight 84.

Also illustrated in FIG. 8 is sidelight 86 which includes no privacycoating deposited thereon. In contrast, sidelight 90 includes privacycoating 96. Sidelight 88 includes a privacy coating 98 which includesfade zone 49 which fades to provide portion 100 of sidelight 88 whichhas no privacy coating 98 deposited thereon. In this fashion, sidelight88 operates to provide an aesthetically pleasing transition betweensidelight 90 which includes a full privacy coating 96 to sidelight 86which contains no privacy coating deposited thereon. The privacy coating98 including fade zone 49 was formed in accordance with the presentinvention. Either of privacy coatings 96 and 98 may be deposited oneither the interior or exterior surfaces of the respective sidelights 90and 88.

As may be appreciated, the present invention is not limited to theprecise embodiment illustrated in FIG. 8, and it is within the scope ofthe present invention to include any of the shade band coatings, privacybands, privacy coatings, aesthetic bands, aesthetic coatings or mixturesthereof on any of the windshield 82, backlight 84 or sidelights 86, 88and 90 illustrated in FIG. 8. For example, as may be appreciated,backlight 84 may have deposited thereon in lieu of or in addition toshade band 94 a privacy coating, (not shown) which privacy coating mayor may not include a fade zone in accordance with the present invention.

The coatings having the fade zone of the present invention may provideother functions in addition to the shading, privacy and/or aestheticfunctions described above, including but not limited to providingultraviolet radiation absorption, low emissivity, or antireflectioncapabilities to glass or other substrates. In addition, the coatings ofthe present invention which include the fade zone may be present for agiven function (e.g. shading) and may be combined with one or more othercoatings to provide the coated article with additional functionality(e.g. low emissivity, color, etc.).

The present invention will be further understood from the description ofthe specific non-limiting example which follows.

EXAMPLE 1

A sheet of clear float glass, measuring about 30 inches (76 cm) inlength by about 25 inches (64 cm) in width by about 0.25 inches (0.64cm) in thickness was heated in an oven to a temperature of about 1150°F. (621° C.). The heated glass sheet was removed from the oven and wasimmediately introduced into a coating station of a spray pyrolysisapparatus on a set of conveying rollers, which caused the glass sheet totravel at a line speed of about 250 inches (635 cm) per minute throughthe coating station.

The coating station included a first exhaust assembly measuring about 12inches (30 cm) in width by about 36 inches (91 cm) in length which wasspaced approximately 15 inches (38 cm) from a second exhaust assemblyhaving roughly the same dimensions. The exhaust assemblies were eachspaced about 2 inches (5.08 cm) above the glass substrate, and each wasoperated at an air flow of about 350 standard cubic feet per minute(hereinafter “scfm”).

Located approximately midway between the exhaust assemblies was acoating composition dispenser. The coating composition dispenserincluded a conventional compressed air atomizing spray nozzle. Thecoating composition dispenser was oriented to dispense a coatingcomposition generally normal to the surface of the glass sheet and waslocated approximately 10 inches (25.4 cm) above the glass sheet. Acoating composition which included a 17% solids concentration of acobalt-chromium-iron acetylacetonate dispersed in water was dispensedthrough the coating composition dispenser at a rate of about 75milliliters (2.5 fluid ounces) per minute and at a pressure of about 8psig. The coating composition was deposited in an generally ellipticalpattern that intersected the glass sheet in an ellipse measuringgenerally about 16 inches (41 cm) along its major axis by about 8 inches(20 cm) along its minor axis. The major axis of the ellipse wasgenerally at about a 45 degree angle to the longitudinal axis of theplane of conveyance of the glass sheet through the coating station.

An gas dispenser which included a conventional compressed air atomizingspray nozzle was oriented to dispense a stream of air generally normalto the surface of the glass sheet. The nozzle was located approximately10 inches (25.4 cm) above the glass sheet. The gas dispenser waspositioned approximately 8 inches (20 cm) away from the coatingcomposition dispenser along a line generally perpendicular to thelongitudinal axis to the plane of conveyance of the glass sheet throughthe coating station. Atmospheric compressed air was dispensed throughthe gas dispenser at a rate of about 5 scfm at a pressure of about 50psig. The air steam pattern was a generally elliptical pattern where itintersected the glass sheet, with the ellipse measuring generally about16 inches (41 cm) by about 8 inches (20 cm). The major axis of theellipse was generally at about a 45 degree angle to the longitudinalaxis of the plane of conveyance of the glass sheet through the coatingstation.

The coating composition dispenser and the gas dispenser formed aninterference effect which caused the pyrolytic deposition of acobalt-chromium-iron metal oxide coating having a gradual, evenlyappearing fade zone. The coating at its thickest point was approximately500 Angstroms thick in an area corresponding generally to that beneaththe coating composition dispenser which extending generally along alongitudinal edge of the glass sheet in along the longitudinal axis ofthe plane of conveyance of the glass sheet through the coating station.The fade zone extended along a line generally perpendicular to thelongitudinal axis of the plane of conveyance of the glass sheet, i.e.across the glass sheet. By visual observation, the coating appeared tofade completely and generally evenly approximately 5 inches (13 cm) fromthe longitudinal edge of the glass sheet, resulting in the formation ofa shade band on the sheet having a fade zone which shade band, includingthe fade zone, was approximately 5 inches (13 cm) wide.

The above example is offered to illustrate the present invention and isnot intended to limit the invention. Various modifications are includedwithin the scope of the invention, which is defined by the followingclaims.

What is claimed is:
 1. An article of manufacture comprising: a floatglass ribbon substrate having at least one major surface; and at leastone pyrolytically deposited coating deposited over the major surface ofthe substrate from the simultaneous directing in spaced apart relationto each other of a spray of a coating composition and a stream of gastoward the surface of the substrate such that an interference effectadjacent the surface of the substrate is produced between them so thatthe interference effect results in the deposited coating comprising afade zone such that the coating has a first limit spaced apart from asecond limit, in which the coating gradually decreases in the parameterselected from the group of: thickness, intensity, and density and anycombination of these from the first thickness, intensity and/or densityat the first limit to a second lesser thickness, intensity and/ordensity at the second limit.
 2. The article of manufacture of claim 1wherein the coating includes a pyrolytically deposited metal oxidecoating.
 3. The article of manufacture of claim 2 wherein the glasssubstrate is a glass sheet selected from the group consisting of anarchitectural transparency, an automotive vehicle windshield, anautomotive vehicle sidelight and an automotive vehicle backlight.
 4. Thearticle of manufacture of claim 3 wherein said coating is selected fromthe group consisting of a shade band, a shade band coating, a privacyband, a privacy coating, an aesthetic band, an aesthetic coating andmixtures thereof.
 5. The article of manufacture of claim 4 wherein saidfade zone is generally parallel to a horizontal axis of the glasssubstrate.
 6. The article of manufacture of claim 4 wherein the fadezone is generally parallel to a vertical axis of the glass substrate. 7.The article of claim 1 wherein said coating comprises at least one metaloxide film.
 8. The article of claim 1 wherein said coating is formedfrom a coating composition selected from the group of at least oneorganometallic compound dissolved in at least one organic solvent, atleast one organometallic compound suspended in a non-aqueous carrier andat least one organometallic compound suspended in an aqueous carrier. 9.The article of claim 1 wherein said coating at least along thelongitudinal axis of the article has little gradient effect for thatportion of the surface of the article over which the coating isdeposited and wherein the coating has a gradient effect observed along aline generally parallel to the surface of the article.
 10. The articleof claim 1 wherein the coating has a first limit spaced apart from asecond limit, in which the coating gradually decreases in the parameterselected from the group of: thickness, intensity, and density and anycombination of these from a first thickness, intensity and/or density atthe first limit to an absence of coating over the substrate at a secondlimit.
 11. The article of manufacture of claim 1 wherein the coating isfrom pyrolytic deposition of the coating composition on the substrate ata temperature in the range of about 1000° F. to about 1500° F. (about538° C. to about 815° C.).
 12. The article of manufacture of claim 1wherein the coating is from the pyrolytic deposition of the coatingcomposition through a thermal barrier resulting from the substratehaving a temperature above the boiling point of the coating compositionfrom a material selected from the group of carrier or solvent present asthe greatest percentage of a component in the coating composition.